I'd place Ahsoka at closer to 16 in S3/S4. It's unclear how much time has passed between S1 and S4. There was a jump, and I think it was about 1.5/2 years (from 22 BBY to 20 BBY), but it's hard to tell.
the clone wars span only three years so she'd be about sixteen at the end of it
Truth. I just checked the dates (to the day), and it spans almost exactly 3 calendar years.
I was thinking it went from January 22 BBY to December 19 BBY, which is four years. But it's May to May.